3184 - 求1-n以内所有数和

<span style="font-family:宋体;font-size:12pt;">【题目描述】</span><span style="font-size:12pt;"></span>

<span style="font-size:12pt;"><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span><span>&nbsp;</span></span><span style="font-family:宋体;font-size:12pt;">给定一个正整数</span><span style="font-size:12pt;">N</span><span style="font-family:宋体;font-size:12pt;">，输出大于等于</span><span style="font-size:12pt;">1</span><span style="font-family:宋体;font-size:12pt;">且小于等于</span><span style="font-size:12pt;">N</span><span style="font-family:宋体;font-size:12pt;">的所有数的和</span><span style="font-size:12pt;"></span>

<span style="font-family:宋体;font-size:12pt;">【输入格式】</span><span style="font-size:12pt;"></span>

<span style="font-size:12pt;"><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span><span>&nbsp;</span></span><span style="font-family:宋体;font-size:12pt;">一个正整数，即</span><span style="font-size:12pt;">N</span>

<span style="font-family:宋体;font-size:12pt;">【输出格式】</span><span style="font-size:12pt;"></span>

<span style="font-size:12pt;"><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span><span>&nbsp;</span></span><span style="font-family:宋体;font-size:12pt;">仅包含一行，即答案</span><span style="font-size:12pt;"></span>

<span style="font-family:宋体;font-size:12pt;">【样例输入】</span><span style="font-size:12pt;"></span>

<span style="font-size:12pt;"><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span><span>&nbsp;</span>10</span>

<span style="font-family:宋体;font-size:12pt;">【样例输出】</span><span style="font-size:12pt;"></span>

<span style="font-size:12pt;">55</span>

<span style="font-family:宋体;font-size:12pt;">【数据规模】</span><span style="font-size:12pt;"></span>

<span style="font-size:12pt;">100%</span><span style="font-family:宋体;font-size:12pt;">的数据，</span><span style="font-family:宋体;font-size:12pt;">n</span><span style="font-family:宋体;font-size:12pt;">≤<span>10000</span></span>

<span style="font-family:宋体;font-size:12pt;">【样例解释】</span><span style="font-size:12pt;"></span>

<span style="font-size:12pt;"><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span><span>&nbsp;</span>1+2+3+4+5+6+7+8+9+10=55</span>

Input

Output

Examples

Input

Output

Solution C

#include <stdio.h>
int a;
int main(void) {
    scanf("%d", &a);
    printf("%d\n", (a + 1) * a / 2);
    return 0;
}

Solution C++

#include<iostream>

using namespace std;

int main()
{
    int a;
    cin>>a;
    cout<<(1+a)*a/2<<endl;
    return 0;
}

Time Limit	1 second
Memory Limit	128 MB

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